This invention relates to new surface impregnated catalysts or skin catalysts as well as a method for making such catalysts.
Catalysts comprising one or more catalytic components supported on suitable carrier or support materials have been employed in a wide variety of industrial operations, such as olefin hydrogenation, isomerization, etc.
Previous methods of preparing such supported catalysts have generally involved soaking the porous support with a solution of catalytic material until the support is substantially saturated with impregnating solution, after which the resulting product is dried and/or calcined and/or chemically reduced to yield a porous mass having a catalytically active material distributed throughout the pores of the support material. Variations of the general procedure have included such as the distribution of a metal containing impregnating solution through all the pores of the carrier, and then reducing the metallic catalytic material that is deposited through all the pores. In the above described preparation, it was deemed advantageous to have the catalytic active material distributed uniformly throughout the porous support.
Some later developments were focused on the controlling of the process of impregnating the catalytically active material into relatively restricted zones located within the support. Impregnating the support material in restricted zones as described in U.S. Pat. No. 2,746,936 is accomplished by the process of (a) partially filling the porous carrier with an inert liquid to physically occupy the filled pores serving to block off such pores during subsequent contact with the impregnating solution. The two liquids are required to be substantially immiscible irrespective of other physical parameters such as surface tension.
A certain type of zoned catalyst called a "skin catalyst" has very desirable properties. Skin catalysts are catalysts where the active material is concentrated near the skin or outer surface of the support material. When the catalytically active material is concentrated near the surface of the support it is in the area where most catalytic activity is carried out and not buried and wasted in the core of the support. These skin catalysts would seem to be most useful as catalysts when used to catalyze materials that do not fully penetrate through to the core of the support or when the reaction in the core of the catalyst is not desirable.
An object of this invention is to provide a catalyst and process of making the catalyst.
A further object is to provide a catalyst and process of making the catalyst whereby the use of the active material in the support is maximized.
Another object of this invention is to provide a skin type catalyst.
Still another object of this invention is to provide an improved process of preparing a skin type catalyst.